Such sensor arrangements are counted as belonging to the state of the art and comprise one or more sensors as well as a housing constructed of one or more plastic injection molded parts. At least a part of the sensor electronics is arranged within the housing, wherein an absorption means which is to absorb and bind the fluid penetrating into the housing is provided for the protection of the electronics from penetrating moisture. The penetration of such moisture or humidity, if at all, can only be prevented with an enormous amount of technical effort, since the plastics applied for the manufacture of the housing are typically not diffusion-tight and let through moisture, even if only to a limited extent, also in the region of the seals, be it between the housing parts or between the sensor and the housing or in the region of the cable feed-though.
Such sensor arrangement is known for example from EP 2 083 250 A1. Hereby, it is the case of a flowmeter which comprises a pot-like housing with a transparent cover or lid and a display arranged therebelow with sensor electronics. The actual sensor with this design is not directly connected to the channel running though the pot-like housing part, but is arranged on the outer side in the form of an ultrasound transducer. Even if the sensor itself here is not directly in contact with the fluid flowing through the channel, moisture can diffuse through the housing wall itself. Moisture can also penetrate into the housing via the seal between the cover and the housing, even if merely in the smallest of quantities. Two different plastics are built in the region of the cover for example, of which the one has a comparatively high diffusion sealedness and the other a high strength, in order to keep such an entry of moisture or humidity as low as possible. Finally, a drying agent (desiccant) is provided within the housing, in order to bind any moisture penetrating into the housing, in order to protect the sensitive sensor electronics from this. Silica gel or calcium chloride is provided here as a desiccant. Such desiccants are counted as belonging to the state of the art and are particularly to be found in packaging. A problem thereby is the fact that on the one hand a sufficient quantity of such a desiccant is to be provided in the housing, and on the other hand that it is ensured that this neither mechanically nor chemically has a negative influence on the adjacent parts.
This problem is amplified with sensor arrangements with a comparatively small housing, with which the sensor itself is in contact with the fluid, as is the case for example with pressure sensors or differential pressure sensors or temperature sensors (EP 2 626 567 A1).